1. Field of the Invention
The present invention relates to a lighting apparatus and an image pickup apparatus equipped therewith.
2. Description of the Related Art
A lighting apparatus used for an image pickup apparatus such as a film camera, digital still camera and video camera is conventionally constructed of a light source and optical members such as a reflector and Fresnel lens that guide a luminous flux generated from this light source forward.
Such a lighting apparatus is available in various designs to efficiently condense the luminous flux irradiated from the light source in various directions within a required irradiation field angle. Especially, there is a proposal of placing optical members using total reflection such as a prism or light guide instead of a Fresnel lens placed in front of the light source so far and thereby improving light condensing efficiency and reducing the size of the apparatus in recent years.
An example of this type of proposal described in Japanese Patent Laid-Open No. 2000-250102 is the one using an optical member provided with a cylindrical lens section having positive refracting property that condenses luminous flux emitted from a light source forward and a prism section that refracts the luminous flux emitted from the light source sideward and then leads the luminous flux forward using a total reflecting surface placed behind. The lighting apparatus according to the proposal in this Publication makes a light distribution from the center of the light source generally uniform by an optical action of the above-described optical member and then irradiates illuminating light from the same plane of outgoing light. This makes it possible to realize a small-sized illumination optical system with high condensing efficiency.
Image pickup apparatuses tend to become much smaller and thinner in recent years than before and there is even a proposal of an extremely thin digital camera such as a card size camera unprecedented by previous arts.
In line with this, a smaller, thinner light source is also an essential condition and there is a strong demand for making commercially feasible an illumination optical system, which will not deteriorate the optical performance under such conditions.
Against such a background, it is also possible to use the lighting apparatus proposed in the above-described Japanese Patent Laid-Open No. 2000-250102 as an ultra-small lighting apparatus.
However, the lighting apparatus proposed in the above-described Publication is still thick in the thickness direction and is not thin enough to be housed in a card size camera. For this reason, this cannot be said as an ideal configuration for a lighting apparatus mounted on a card type camera or card type electronic flash.